This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. With the growing acceptance of Linux as a versatile and common operating system for x86 based machines, we have undertaken a linux port of some of our most commonly used simulation and non-linear least-squares (NLLS) fitting routines in order to facilitate their dissemination among the ESR community. This is particularly important for the NLLS fitting routines with graphical display of the spectrum and fit that we use with our 1D spectra. The original package was written for the X-windows system and rs6000 architecture. Given that the X-window system is quite common in the linux community, it was a relatively straightforward task to port the graphical interface. Furthermore, the computationally intensive sections of the package with extensive calls to linear algebra (LA) routines are written in such a way that they make no use of commercial LA packages and their attendant restrictions on subsequent dissemination of the source code. Thus, the entire package consisting of the source code and makefile compiles and runs "out of the box". The port did require some modifications of the original computational sections of the package in order to ensure consistency of array boundaries. It was found that the original 1D simulation software was very robust in this regard. In order to facilitate the dissemination of these new software packages, we have placed them on the center's ftp site, accessible through our homepage. This new software package benefited from extensive testing at the recent hands-on ESR spectral simulation workshop sponsored by ACERT. User feedback led to a number of suggestions for improvements to the package, and these are being incorporated as time and other resources permit.